Rise of Byzantium

The Rise of Byzantium was a period from 533 to 628 AD, during which the former Eastern Roman Empire formed a new empire in its own right, the Byzantine Empire. The two great Byzantine emperors who led the resurgence of Byzantium were Justinian I and Heraclius; Justinian succeeded in reconquering much of the former Western Roman Empire before these gains were lost to further barbarian invasions, while Heraclius defended the empire's eastern borders against the Sassanid Persians. Byzantium's rise would come to an end duuring the 630s and 640s, when the rise of the Muslim Rashidun Caliphate in the Arabian Peninsula eclipsed the might of the Romans.

Background
Byzantium - beside the Bosphorus River where the city of Istanbul now stands - was founded as a colony by Greek traders in 661 BCE. Byzantium was an important trading center, pivotally placed between Greece and the Mediterranean on one side and the rich cities of western Asia on the other. The conquests of Alexander brought the Middle East into the Greek cultural sphere. It remained so after the Roman conquest of the 2nd century BC. By the 4th century AD the  economic base of the Roman Empire had moved to the east. The first Christian emperor, Constantine the Great, built his city there, naming it "Constantinople" after himself. His successor, Emperor Theodosius II (408-450), bolstered the capital's defenses, building what became known as the Theodosian Wall. Constantinople would soon overtake Rome in importance, but when the Western Roman Empire fell to barbarians in the 5th century, Constantine's city was left the unrivaled center of a primarily Asian "Roman" empire.

History
The Arabs called them the "Rum." Their city may have been founded by the Greeks, it may have looked eastward into Asia; but the Byzantines always saw themselves as Romans. Their empire perpetuated that of Rome, even if its western states - and its nominal capital - had been routed by barbarians. This applied in the military sphere too: the old legionary structures were kept, as were the old Roman values of order, discipline, and logistical efﬁciency. For a while, in the 6th century, it seemed possible the lost territories might be recovered. The emperor Justinian I (r. 527-565), famous for his codiﬁcation of Roman law, laid out plans for a more ambitious project: the renovatio imperii, or "renewal of the empire."

Into Africa
That this could be more than an empty dream owed much to the daring and skill of Justinian's military commander, Belisarius. Born around 505, he is believed to have been of Greek or Thracian ancestry. In 528, having risen through the ranks of the Byzantine army, Justinian made him his commander in the Iberian War (fought not in the Iberian Peninsula but in the little Caucasian kingdom of Iberia). Byzantium had been locked in conﬂict with Persia's Sassanid rulers over this country for some years, but the hostilities had now turned into open war. Belisarius triumphed at Dara in 530, but after a stalemate at Callinicum the following year, the Byzantines and Persians agreed an inconclusive peace. Justinian still felt strong enough to embark upon a new campaign in a different theater and sent Belisarius out to conquer the Vandal kingdom in what for centuries had been the Roman province of Africa.

Though now established in eastern Algeria and Tunisia, the Vandals were of Germanic origin. In 429, with Rome's western empire in turmoil, they had swept southward through Spain before crossing the Straits of Gibraltar. Sacking Roman Carthage, the Vandals soon set up their own capital there. Conﬁned to the coastal plain, the new Vandal kingdom was insigniﬁcant in terms of territory. However, it made the perfect base for onslaughts across the Mediterranean: in 455 the Vandals had sacked Rome itself, and they continued to torment the eastern empire. In 533 Justinian dispatched his invasion-ﬂeet. Belisarius's army was small: he had some 15,000 troops at his disposal, of which 10,000 were infantry and the rest cavalry. Victory came swiftly at the battle of Ad Decimum. Fortune favored the Byzantines. The city of Carthage was captured, and Africa was recovered.

Power Struggle
In 535, exhilarated by this success, Justinian sent Belisarius to reclaim the Italian "homeland," at this time under the occupation of the Ostrogoths. By 536 Rome had been secured. However, the war for the rest of Italy was not to be so easy: in the following years, the balance of power in the peninsula shifted back and forth through a gruelling series of pitched battles and city-sieges. In 540 Belisarius recaptured the Ostrogoth base, Ravenna, making it the capital of a re-established western empire. However, these gains were hard to hold. The Goths were not beaten and by the early 550s were resurgent in Italy. Problems were mounting for the empire: in 568 Italy was invaded from the north by the Germanic Lombards, while in 577 the Slavs and Avars invaded the Balkans from the north and east.

In Asia, meanwhile, the war with Persia had resumed in 572. It would continue intermittently for 50 years, shaping the Byzantine war machine. Persia's strength in cavalry had to be countered. The Sasanids could deploy thousands of cataphracts, armored horsemen who charged with lances raised, smashing into the enemy with a force that even the toughest, most disciplined infantrymen could not withstand. After the shock of the ﬁrst impact came the terrifying confusion as the units of cataphracts drew their bows and showered arrows all around.

Fighting Back
The Byzantines saw no alternative but to match the Persian threat directly. They assembled cataphract units of their own, reinforcing them with light and heavy infantry. The Byzantines were short of people. Most of their soldiers were foederati, recruited from the many barbarian peoples who were bound by treaty to the Byzantine cause; others were mercenaries. But all served the empire well. The Persians were kept at bay and at last, in 627, the armies of Emperor Heraclius scored a daring victory over the Sassanids at Nineveh, Iraq. But the relief this brought was a cruel illusion. The exhausted imperial armies had succeeded only in clearing the way for invasion by the Arabs.

That Constantinople held out for the next 500 years against more Arab assaults is testimony to the empire’s naval power, and to the potency of "Greek Fire," the great Byzantine secret weapon. Believed to have been a blend of burning oil and tar propelled by a pump - a sort of medieval ﬂamethrower - it played havoc with the enemy in an age of wooden ships.

Aftermath
Decades of war in western Asia had left both Byzantium and Persia drained. Neither was able to hold up the expansion of the Arabs through the 7th century. The decline of the Byzantine empire from this time on was inexorable, and it was permanently on the defensive. But long after the bulk of its land-territories had gone, it remained an important naval power. In between attacks by the Arabs came assaults by many different enemies, from the Varangians (Ukrainian-based Vikings) to the Bulgars. Wars with these groups in the 9th, 10th, and 11th centuries saw Constantinople under threat, while the states in Italy and Sicily were taken by the Normans in the 11th century. In 1204, Constantinople was sacked by the armies of the Fourth Crusade. It fell to the Ottoman Turks in I453, and became their capital for almost 600 years.